Techniques for evaluating an image have been proposed in the prior art. For example, Patent Literature 1 proposes a technique of objectively evaluating an evaluation-target image resulting from processing an original image using entropy. This technique necessitates the un-processed original image as a comparing image in addition to the evaluation-target image.
Additionally, Non Patent Literature 1 reports a study on pseudo-Hilbert scan satisfying the condition that neighboring pixels on a path are also neighbors in a rectangular image while going through all pixels of the rectangular image for making progress in applications in image compression.